The National Aeronautics and Space Administration (NASA) is presently embarked on a project to design, construct and deploy a permanently manned orbiting space station. (See "Space Station: The Next Logical Step," Aerospace America, Sept. 1984, pp 47-55 by James M. Beggs.) Such a station is critically important to the advancement of the United States as a world leader because it represents a major step in the commercialization of space and its eventual colonization. Moreover, it will--for the first time in human civilization--provide scientists with a gravity-free environment for conducting fundamental experiments that could eventually lead to revolutionary scientific and technological breakthroughs.
Although it is impossible to list all of the functions that a permanently manned orbiting space station will be engaged in, and the benefits to be derived therefrom, it is important from a design point of view, to understand some of its major functions. One of the most important functions in terms of immediate economic benefits will involve utilizing the station as an "orbiting service station" where previously deployed, but malfunctioning satellites can be repaired, refurbished and redeployed. Another function will involve providing a gravity-free environment for conducting basic scientific experiments in the life and physical sciences. It will also provide a gravity-free environment for manufacturing new materials (such as growing ultra-pure single crystals for computer chips) and developing new drugs for curing various diseases.
The station will also provide a platform for conducting extensive telescopic observations of the Earth's surface by human operators in real-time. Thus, selected areas could be immediately identified for closer inspection using high-power telescopes that will enable photographs to be taken with ultra-high resolution. The instrumentation could include passive infrared sensors for night observations, along with active high-power radar systems. These ground observations would also include extensive meteorological observations resulting in more accurate global weather forecasts.
The space station will also enable trained astronomers to conduct extensive astronomical observations using the most sophisticated equipment. Since the station moves above the atmosphere, the entire electromagnetic spectrum of the universe will be available for detailed investigation. The instrumentation will include powerful optical telescopes, gamma ray and x-ray sensors, infrared telescopes and a whole array of support instrumentation. The least known astronomical objects such as quasars and black holes could be studied that might lead to the discovery of revolutionary theories for generating unlimited amounts of energy.
An advanced manned space station could be equipped with multiple hangars in which completely new satellites could be assembled. A sufficiently large space station could be utilized as a home base for astronaut construction workers assembling huge structures in orbit such as radio antennas or solar power stations. Such stations could also serve as "jumping-off points" for trips to the Moon or to other celestial bodies.
It is difficult to predict or describe all of the immediate economical benefits that a permanently manned orbiting space station will provide. But this much is certain--a permanently manned orbiting space station will give the United States undisputed technological leadership of the world. This, in turn, will make the Earth a safer place to live by significantly reducing the risk of global war.
During the past two years several NASA contractors have been working on, and submitting their design proposals for the first permanently manned orbiting space station. Under the ground rules laid down by NASA, the space station must be compatible with the existing reusable ground-to-orbit Shuttle vehicle. Thus, all of the structural components must be transported to to orbit inside the Shuttle's cargo bay. This cargo bay is approximately cylindrical with a length of 18.29 m (60 ft) and a diameter of 4.57 m (15 ft). The maximum payload mass that the vehicle can deliver to a 28.5.degree. inclination 200 km high circular parking orbit is 30,000 kg (66,140 lbs).
Another important ground rule requires the station to be easily expandable into a larger station by adding more structural components of essentially the same basic design. Thus, the initial space station has to have a basically "modular" design.
In view of the overall budgetary constraints (8 billion dollars) it was immediately assumed that the only practical method for constructing the space station would be to deliver separate prefabricated habitation and support modules to orbit, one-by-one inside the Shuttle cargo bay and assemble them in orbit after all of the modules are delivered. Thus, each module was designed to be cylindrical with an outside diameter not exceeding 4.57 m (15 ft) and an overall length of 13.72 m (45 ft). There would be five pressurized modules altogether comprising two modules for living quarters (i.e. habitation modules), two laboratory modules, and one logistics module. The method selected for generating electric power involved constructing a large array of solar cells. The solar array would be connected to the pressurized modules by complicated open truss-type frames which provide the basic structural support. All of these basic design features were incorporated into each of the various designs. They differed only in their final configurations (i.e., they differed only in the relative positions of the basic components). Since the solar array and parts to the structural frame required two additional Shuttle flights, each design required a total of seven Shuttle flights to assemble.
Of all of the various designs submitted to date, the so-called "Power Tower" design of Rockwell International is the favorite. (See "Power Tower: Living in Orbit," Science Digest, June 1985 by Ben Bova.)
In view of the limited size of the habitation cylinders, it is impractical to provide any type of artificial gravity by rotating them. Hence, in the current design, the crew will be forced to live in a weightless state over extended time intervals lasting up to 90 days or more. However, recent medical data accumulated over the past three years with numerous Shuttle flights indicates that about 50% of the astronauts subjected to prolonged weightlessness can be expected to suffer severe "space-sickness". But astronauts are among the most physically fit humans in the general population. If 50% of these people can be expected to suffer space sickness, it is highly likely that the vast majority of the general population will not be able to endure extended periods of weigthlessness. Thus, it is highly likely that the most valuable personnel brought up to work in the currently planned space station--such as highly skilled professional astronomers, biologists, chemists, physicists, etc., recruited from leading universities--will be rendered useless by space sickness brought about by prolonged exposure to weightlessness.
This situation poses an ominous threat that could undermine the entire United States effort to build a permanently manned space station because the current plans are based on a design that does not provide any artificial gravity. Moreover, since all of the current NASA plans for constructing much larger space stations in the future are based upon expanding the initial design, they will also be incapable of providing artificial gravity. Thus, there exists the real possibility that after spending many billions of dollars constructing a permanently manned orbiting space station, it may be rendered useless by the simple fact that most of the highly skilled scientists brought up to it become totally incapacitated by space sickness brought about by prolonged exposure to weightlessness.
The most important reason that is used to argue the necessity for constructing a permanently manned orbiting space station is based upon the premise that humans can accomplish tasks in orbit well beyond the capability of automated systems. But it is obvious that if most of the humans living in a space station eventually become incapacitated due to space sickness, this argument is invalid. Is should be pointed out, however, that NASA is attempting to circumvent this critical problem by developing drugs to overcome space sickness. But the weightless state is so new and so vastly different from anything previously experienced by man on Earth, this approach may not be successful.
The root of the problem lies in the assumption that the habitation modules must be constructed on the ground and transported inside the Shuttle cargo bay as complete, prefabricated, living quarters because this requirement forces the modules to be too small for generating any artificial gravity by rotation. But this prefabricated modualr design approach is believed to be an absolute prerequisite for constructing all low cost pressurized space stations because there is currently no known method for constructing rigid, thick-walled, continuous surface, pressurized structures in orbit for manned space stations other than the well known method of transporting completed hull sections and assembling them in orbit one-by-one which will be extremely expensive.
There is another important disadvantage that is inherent in the prefabricated modular design approach. It results in a very poor utilization of the Shuttle's full weight lifting capability. For example, it is estimated that the total mass of the complete Power Tower space station will be 120,000 kg (265,000 lbs). On a strictly weight lifting basis, this mass could be delivered to low Earth orbit (LEO) in only four Shuttle flights instead of the seven that are required. Seven Shuttle flights will be capable of delivering 210,000 kg (463,000 lbs) which is almost twice the mass estimate for the Power Tower.
The present disclosure sets forth an entirely new permanently manned orbiting space station that provides a large artificial gravity environment for the living quarters. It is based upon a fundamentally new low cost method for constructing large, thick-walled, continuous surface pressurized structures in orbit using robotics.